CD25 Expression in B Lymphoblastic Leukemia/Lymphoma Predicts t(9;22)(q34;q11)/Philadelphia Chromosome Translocation (Ph) and Is Associated With Residual Disease in Ph-Negative Patients

OBJECTIVES: CD25 expression is associated with t(9;22)(q34;q11)/Philadelphia chromosome translocation (Ph); BCR-ABL1 rearrangement in B lymphoblastic leukemia/lymphoma (B-LL). However, the significance of CD25 expression in Ph negative (Ph-) B-LL regarding residual disease (RD) and genetic abnormalities is largely unknown. METHODS: CD25 expression by flow cytometry (FC) was correlated with Ph status in 95 newly diagnosed B-LL patients and with RD status in day 29 marrow measured by FC in the context of cytogenetic risk stratification in Ph- patients. RESULTS: CD25 expression was greater in Ph positive (Ph+) patients (80%) than in Ph- patients (17%), predicting Ph+ with 80% sensitivity and 86% specificity. In Ph- patients, CD25 expression (in 14 patients, 16%) was associated with RD in the cytogenetic intermediate-risk group: detectable RD in 50% of CD25+ patients vs 14% of CD25- patients. Interestingly, one CD25+/Ph- patient had a Ph-like genotype ( ZC3HAV1-ABL2 rearrangement), and another had dual MYC-IGH and BCL2-IGH rearrangements. CONCLUSIONS: Our findings not only confirm the predictive power of CD25 expression for Ph+ but also demonstrate that CD25 expression is associated with RD (a biomarker correlated with prognosis) in Ph- patients. The latter finding is likely associated with underlying molecular abnormalities, including Ph-like genotype.